The dynamic memory essentially requires a reset period. In the conventional dynamic memory in which all of the portions are reset at one time, the cycle time is the sum of a period (access time) including from the start of access of a portion to which the access is made at first to the completion of access of a portion to which the access is finally made and a reset time. On the other hand, the static memory does not require resetting. Therefore, the cycle time of the static memory is nearly equal to the access time. Thus, the dynamic memory having a long cycle time is capable of writing and reading data in a quantity smaller than that of the static memory within a unit period of time.